Shaw, L.J. and Burns, R.G. (2004) Enhanced mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid in soil from the rhizosphere of Trifolium pratense. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 70 (8). pp. 4766-4774. ISSN 0099-2240.
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Enhanced biodegradation in the rhizosphere has been reported for many organic xenobiotic compounds, although the mechanisms are not fully understood. The purpose of this study was to discover whether rhizosphere-enhanced biodegradation is due to selective enrichment of degraders through growth on compounds produced by rhizodeposition. We monitored the mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid (2,4-D) in rhizosphere soil with no history of herbicide application collected over a period of 0 to 116 days after sowing of Lolium perenne and Trifolium pratense. The relationships between the mineralization kinetics, the number of 2,4-D degraders, and the diversity of genes encoding 2,4-D/alpha-ketoglutarate dioxygenase (tfdA) were investigated. The rhizosphere effect on [(14)C]2,4-D mineralization (50 microg g(-1)) was shown to be plant species and plant age specific. In comparison with nonplanted soil, there were significant (P < 0.05) reductions in the lag phase and enhancements of the maximum mineralization rate for 25- and 60-day T. pratense soil but not for 116-day T. pratense rhizosphere soil or for L. perenne rhizosphere soil of any age. Numbers of 2,4-D degraders in planted and nonplanted soil were low (most probable number, <100 g(-1)) and were not related to plant species or age. Single-strand conformational polymorphism analysis showed that plant species had no impact on the diversity of alpha-Proteobacteria tfdA-like genes, although an impact of 2,4-D application was recorded. Our results indicate that enhanced mineralization in T. pratense rhizosphere soil is not due to enrichment of 2,4-D-degrading microorganisms by rhizodeposits. We suggest an alternative mechanism in which one or more components of the rhizodeposits induce the 2,4-D pathway.
|Additional information:||0099-2240 (Print) Journal Article Research Support, Non-U.S. Gov't|
|Uncontrolled keywords:||2,4-Dichlorophenoxyacetic Acid/*metabolism Alphaproteobacteria/classification/*enzymology/genetics/isolation & purification Biodegradation, Environmental Carbon Radioisotopes/*metabolism Ketoglutarate Dehydrogenase Complex/genetics/metabolism Lolium/growth & development Molecular Sequence Data Plant Roots/*microbiology Polymerase Chain Reaction Polymorphism, Single-Stranded Conformational Sequence Analysis, DNA Soil/analysis *Soil Microbiology Species Specificity Trifolium/growth & development/*microbiology|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||Sue Davies|
|Date Deposited:||10 Sep 2008 14:42|
|Last Modified:||14 Jan 2010 14:25|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/6744 (The current URI for this page, for reference purposes)|
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